1. Field of the Invention
The present invention relates to an error correction device, an encoder, a decoder, a method, and an information storage device for correcting errors in data which is to be transmitted in an m-bit-error-dominant sequence, and particularly relates to an error correction device, an encoder, a decoder, a method, and an information storage device for correcting errors in data which is to be transmitted in a 1-bit error-dominant recording/reproducing system such as a magnetic disk apparatus.
2. Description of the Related Arts
Conventionally, a Reed Solomon code (RS code) has been used as an ECC code, which is an error correcting code, in a magnetic disk apparatus or an optical disk apparatus. Under a circumstance in which long errors apt to occur like a conventional PRML channel, the Reed Solomon code can be assumed as an optimal error correcting code. Meanwhile, a low-density parity check code, i.e., LDPC code attracts attention as an error correcting technique of the next generation in magnetic disk apparatuses, and LDPC codes for magnetic disk apparatuses are actively studied. The LDPC code is remarkably excellent in the performance of correcting random errors. However, since the LDPC code involves a problem of, for example, error floor, error correction by an ECC code is required after decoding by the LDPC code. Herein, the error floor is referred to as a phenomenon in which, in an error correcting code, while the decoding error rate is rapidly improved in a low SNR (signal-to-noise power ratio) region along with decrease of noise power, the error rate is scarcely improved in a high SNR region even though the noise power is reduced.
However, 1-bit errors are predominant in the errors of data output in decoding by such conventional LDPC code, and 1 symbol is allocated to a 1-bit error in error correction by the Reed Solomon code; therefore, there is a problem that the maximum number of correctable 1-bit errors is limited, and efficient 1-bit error correction can not be performed.